A transformer has become an essential electronic component for voltage regulation into required voltages for various kinds of electric appliances. Referring to FIG. 1, a schematic exploded view of a conventional transformer is illustrated. The transformer 1 principally comprises a magnetic core assembly 11, a bobbin 12, a primary winding coil 13, a secondary winding coil 14 and an insulating tape 15. The bobbin 12 comprises a first side plate 121, a second side plate 122 and a winding member 123. The insulating tape 15 is wound around the middle portion of the winding member 123. The winding member 123 is divided into a first winding section 1231 and a second winding section 1232, which are located at bilateral sides of the insulating tape 15. The primary winding coil 13 and the secondary winding coil 14 are wound around the first winding section 1231 and the second winding section 1232, respectively. The primary winding coil 13 and the secondary winding coil 14 are separated from each other by the insulating tape 15, thereby providing a desired creepage distance.
Although the transformer 1 is effective for power conversion, there are still some drawbacks. For example, during power conversion of the transformer 1, the magnetic core assembly 11 is readily charged and thus suffered from electromagnetic interference (EMI). For suppressing EMI, the outer periphery of the transformer 1 is usually shielded by a copper foil (not shown) according to an electrostatic screening effect. The arrangement of the copper foil may increase the fabricating cost of the transformer. Furthermore, the procedure of winding the copper foil around the outer periphery of the transformer 1 is very labor-intensive and time-consuming and thus the throughput is insufficient.
Therefore, there is a need of providing an improved transformer so as to obviate the drawbacks encountered from the prior art.